1. Field of the Invention
The present invention relates to a pneumatic exercising device and more particularly to such a device which is operable to duplicate the superior operative characteristics of "weight type" exercising machines while avoiding the undesirable characteristics of these and other exercising machines in a device which is compact, dependable and readily adjustable for selection of both the desired extent and character of the resistance force.
2. Description of the Prior Art
The art in the area of exercising equipment is extensive. Many devices have been developed of the "weight type" wherein weights are employed in the resistance to the exertion of muscular force. Perhaps the simplest of these are barbells, but a host of machines of this type have been developed which employ weight stacks of a variety of types against which muscular force is exerted in exercising to achieve or maintain muscular development. Machines of the "weight type" suffer from several common deficiencies which detract from their desirability. Such machines are normally rather cumbersome and expensive. They do not possess the infinite degree of adjustability which would be desired. Perhaps more importantly for certain exercising operations, these machines, by their use of weight stacks, create an inertia of movement once the lifting operation has begun which does not require optimum use of the muscles throughout the exercising stroke.
A variety of types of hydraulic machines, such as that of the applicant's U.S. Pat. No. 4,050,310, have been developed. In many instances they have been developed in an effort to overcome some of the deficiencies experienced with the "weight type" variety of exercising machine. Hydraulic machines overcome many of these disadvantages, but possess certain disadvantages of their own. Hydraulic machines do not retain some of the advantages in the "weight type" exercising machines. For example, in a "weight type" machine, if the selected total weight is beyond the capability of the person who is to exercise, he cannot operate the machine. The greatest weight lifted using the machine thus becomes an index of the capability of the operator. Accordingly, such machines are quite useful, for example, in training for weight lifting competition in which barbells are used. However, in a hydraulic machine virtually any hydraulic resistance force can be overcome by the steady application of muscular force. Additionally, and perhaps more importantly, hydraulic machines do not permit the development of the speed with which exercising is performed nor do they simulate the necessity in "weight type" machines of working against the resistance force on the return stroke to the rest position. Furthermore, hydraulic machines, as in "weight type" machines, create an inertia of motion which does not demand the maximum effort throughout the exercising stroke.
Therefore, it has long been known that it would be desirable to have an exercising device which simulates the desired characteristics of a "weight type" exercising machine permitting the operator to increase both the magnitude of weight effectively lifted and the speed with which such weight can be lifted; which does not create an inertia of motion demanding less of the operator after movement has begun thereby insuring full muscular effort throught the stroke; and which is compact, dependable and permits a virtually infinite range of ajustment of the extent and character of the resistance force.